Transmission of light through waveguides has been used for many types of communications applications. Light signals offer potential advantages over electronic signals. Light sources can be created from semiconductor devices, including semiconductor devices such as light emitting diodes and laser diodes.
Optical fiber is used as a transmission medium for light signals. A single fiber is capable of carrying several different modulated signals within it at one time. For instance, wavelength division multiplexing may divide a bandwidth of the fiber into different channels (e.g., each channel containing a small range of wavelengths) and thus may transmit several different wavelengths (e.g., signals) of light at once. Using such a system requires sources for the different wavelengths.